Featured Research

from universities, journals, and other organizations

World's best measurement of W boson mass points to Higgs mass and tests Standard Model

March 2, 2012
DOE/Fermi National Accelerator Laboratory
The latest measurement of the mass of the W boson from the Tevatron experiments. The new combined result is twice as precise as the previous world average, and places limits on the mass of the Higgs consistent with the limits from direct searches at the LHC and Tevatron.

The new CDF and Dzero combined result for the W boson mass (vertical section of green oval), combined with the world's best value for the top quark mass (horizontal section of green oval), restricts the Higgs mass requiring it to be less than 152 GeV/c2 with 95 percent probability. Direct searches have narrowed the allowed Higgs mass range to 115-127 GeV/c2. The grey bar shows the remaining area the Higgs could reside in.
Credit: Image courtesy of DOE/Fermi National Accelerator Laboratory

The world's most precise measurement of the mass of the W boson, one of nature's elementary particles, has been achieved by scientists from the CDF and DZero collaborations at the Department of Energy's Fermi National Accelerator Laboratory. The new measurement is an important, independent constraint of the mass of the theorized Higgs boson. It also provides a rigorous test of the Standard Model that serves as the blueprint for our world, detailing the properties of the building blocks of matter and how they interact.

The Higgs boson is the last undiscovered component of the Standard Model and theorized to give all other particles their masses. Scientists employ two techniques to find the hiding place of the Higgs particle: the direct production of Higgs particles and precision measurements of other particles and forces that could be influenced by the existence of a Higgs particles. The new measurement of the W boson mass falls into the precision category.

The CDF collaboration measured the W boson mass to be 80387 +/- 19 MeV/c2. The DZero collaboration measured the particle's mass to be 80375 +-23 MeV/c2. The two measurements combined along with the addition of previous data from the earliest operation of the Tevatron produces a measurement of 80387 +- 17 MeV/c2, which has a precision of 0.02 percent.

These ultra-precise, rigorous measurements took up to five years for the collaborations to complete independently. The collaborations measured the particle's mass in six different ways, which all match and combine for a result that is twice as precise as the previous measurement. The results were presented at seminars at Fermilab over the past two weeks by physicists Ashutosh Kotwal from Duke University and Jan Stark from the Laboratoire de Physique Subatomique et de Cosmologie in Grenoble, France.

"This measurement illustrates the great contributions that the Tevatron has made and continues to make with further analysis of its accumulated data," said Fermilab Director Pier Oddone. "The precision of the measurement is unprecedented and allows rigorous tests of our underlying theory of how the universe works."

The new W mass measurement and the latest precision determination of the mass of the top quark from Fermilab triangulate the location of the Higgs particle and restrict its mass to less than 152 GeV/c2 .This is in agreement with the latest direct searches at the LHC, which constrain the Higgs mass to less than 127 GeV/c2, and direct-search limits from the Tevatron, which point to a Higgs mass of less than 156 GeV/c2, before the update of their results expected for next week.

"The Tevatron has expanded the way we view particle physics," said CDF co-spokesperson and Fermilab physicist Rob Roser. "Tevatron experiments discovered the top quark, made precision measurements of the W boson mass, observed B_s mixing and set many limits on potential new physics theories."

The new measurement comes at a pivotal time, just days before physicists from the Tevatron and the Large Hadron Collider at CERN will present their latest direct-search results in the hunt for the Higgs at the annual conference on Electroweak Interactions and Unified Theories known as Rencontres de Moriond in Italy. The CDF and DZero experiments plan to present their latest results on March 7.

"It is a very exciting time to analyze data at particle colliders," said Gregorio Bernardi, DZero co-spokesperson and physicist at the Laboratoire de Physique Nuclιaire et de Hautes Energies in Paris. "The next few months will confirm if the Standard Model is correct, or if there are other particles and forces yet to be discovered."

The existence of the world we live in depends on the W boson mass being heavy rather than massless as the Standard Model predicts. The W boson is a carrier of the electroweak nuclear force that is responsible for such fundamental process as the production of energy in the sun.

"The W mass is a very distinctive feature of the universe we live in, and requires an explanation," said Giovanni Punzi, CDF co-spokesperson and physicist from the University of Pisa. "Its precise value is perhaps the most striking evidence for something "out there" still to be found, be it the Higgs or some variation of it."

"The measurement of the W boson mass will be one of the great scientific legacies of the Tevatron particle collider," added DZero co-spokesperson and Fermilab scientist Dmitri Denisov.

Story Source:

The above story is based on materials provided by DOE/Fermi National Accelerator Laboratory. Note: Materials may be edited for content and length.

Cite This Page:

DOE/Fermi National Accelerator Laboratory. "World's best measurement of W boson mass points to Higgs mass and tests Standard Model." ScienceDaily. ScienceDaily, 2 March 2012. <www.sciencedaily.com/releases/2012/03/120302132428.htm>.
DOE/Fermi National Accelerator Laboratory. (2012, March 2). World's best measurement of W boson mass points to Higgs mass and tests Standard Model. ScienceDaily. Retrieved October 2, 2014 from www.sciencedaily.com/releases/2012/03/120302132428.htm
DOE/Fermi National Accelerator Laboratory. "World's best measurement of W boson mass points to Higgs mass and tests Standard Model." ScienceDaily. www.sciencedaily.com/releases/2012/03/120302132428.htm (accessed October 2, 2014).

Share This

More Matter & Energy News

Thursday, October 2, 2014

Featured Research

from universities, journals, and other organizations

Featured Videos

from AP, Reuters, AFP, and other news services

Japan Looks To Faster Future As Bullet Train Turns 50

Japan Looks To Faster Future As Bullet Train Turns 50

Newsy (Oct. 1, 2014) — Japan's bullet train turns 50 Wednesday. Here's a look at how it's changed over half a century — and the changes it's inspired globally. Video provided by Newsy
Powered by NewsLook.com
US Police Put Body Cameras to the Test

US Police Put Body Cameras to the Test

AFP (Oct. 1, 2014) — Police body cameras are gradually being rolled out across the US, with interest surging after the fatal police shooting in August of an unarmed black teenager. Duration: 02:18 Video provided by AFP
Powered by NewsLook.com
Raw: Japan Celebrates 'bullet Train' Anniversary

Raw: Japan Celebrates 'bullet Train' Anniversary

AP (Oct. 1, 2014) — A ceremony marking 50 years since Japan launched its Shinkansen bullet train was held on Wednesday in Tokyo. The latest model can travel from Tokyo to Osaka, a distance of 319 miles, in two hours and 25 minutes. (Oct. 1) Video provided by AP
Powered by NewsLook.com
Robotic Hair Restoration

Robotic Hair Restoration

Ivanhoe (Oct. 1, 2014) — A new robotic procedure is changing the way we transplant hair. The ARTAS robot leaves no linear scarring and provides more natural results. Video provided by Ivanhoe
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.


Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News


Free Subscriptions

Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile

Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?

Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins